(1) Biological soil crusts (biocrusts) are microecosystems consisting of prokaryotic and eukaryotic microorganisms growing on the topsoil. This study aims to characterize changes in the community structure of biocrust phototrophic organisms along a dune chronosequence in the Baltic Sea compared to an inland dune in northern Germany. (2) A vegetation survey followed by species determination and sediment analyses were conducted. (3) The results highlight a varying phototrophic community composition within the biocrusts regarding the different successional stages of the dunes. At both study sites, a shift from algae-dominated to lichen- and moss-dominated biocrusts in later successional dune types was observed. The algae community of both study sites shared 50% of the identified species while the moss and lichen community shared less than 15%. This indicates a more generalized occurrence of the algal taxa along both chronosequences. The mosses and lichens showed a habitat-specific species community. Moreover, an increase in the organic matter and moisture content with advanced biocrust development was detected. The enrichment of carbon, nitrogen, and phosphorus in the different biocrust types showed a similar relationship. (4) This relation can be explained by biomass growth and potential nutrient mobilization by the microorganisms. Hence, the observed biocrust development potentially enhanced soil formation and contributed to nutrient accumulation.

Mangrove forests and seagrass meadows provide critical ecosystem services, including the accumulation of "blue carbon." Plants' functional traits could influence this blue carbon accumulation. To test for interactions among functional traits and blue carbon accumulation, we conducted a study in connected mangrove-seagrass coastal ecosystems in southeast Florida (USA). We quantified how plants' above-ground traits correlated with sediment nutrient content, and how changes in traits along inland-to-coastal gradients influenced inorganic and organic carbon storage potential. Physical traits of Thalassia testudinum were higher at sites with higher sediment phosphorus (SP) and nitrogen (SN) concentrations. Sediment organic carbon concentrations were positively correlated to T. testudinum physical traits. Root density, pneumatophore abundance, specific leaf area, leaf toughness, leaf nitrogen, and phosphorus content were positively correlated with SN concentrations in the mangrove forest coastal fringe. Mangrove leaf thickness and root complexity index were negatively correlated with SP concentrations in the coastal fringe. Our results also indicate that seagrass above-ground traits and blue carbon were strongly correlated in areas with higher sediment nutrient concentrations. Moreover, mangrove root complexity is coupled with phosphorus limitation, whereby highly complex root systems develop with decreasing phosphorus concentrations. Distinct functional traits of plants drive variation in carbon retention capacity even in interconnected ecosystems.

Aim Biological soil crusts (biocrusts) are autonomous ecosystems consisting of prokaryotic and eukaryotic microorganisms growing on the topsoil. They colonize global climatic zones, including temperate dunes. This study examines changes in the community structure of biocrust phototrophic organisms along a dune chronosequence at the Baltic Sea compared to an inland dune in Northern Germany. Methods The community composition and their shift between different successional stages of dune development were related to physico-chemical sediment properties. A vegetation survey followed by species determination and sediment analyses were conducted. Results The findings highlighted a varying phototrophic community composition regarding the different dune successional stages. In both study sites, a shift from algae-dominated biocrusts in younger to lichen- and moss-dominated biocrusts in later successional dune types was observed. This underlined a zonation from young to mature biocrusts along a dune chronosequence. The algae community of the two study sites shared 50% of the identified species while the moss and lichen community shared less than 15%. This indicates a more generalized occurrence of the algal species along both dune chronosequences. The mosses and lichens showed a habitat-specific species community. Moreover, an increase in the organic matter and moisture content with advanced biocrust development was detected. The enrichment of phosphorus in the different biocrust types showed a similar relationship. Conclusion This relation is explainable by biomass growth and potential phosphorus mobilization from the underlying sediment by microorganisms. The observed biocrust development supported nutrient enrichment and biomass accumulation and potentially maintained in turn soil formation.